1. Field of the Invention
The present invention relates to a separating machine which separates a thinned semiconductor substrate from a holding substrate after the semiconductor substrate has been bonded to the holding substrate with a thermoplastic resin and a back surface treatment, including the thinning of the semiconductor substrate, is carried out. The present invention also relates to a separation method.
2. Description of Related Art
In recent years, electronic devices have been desired to be decreased in thickness or in weight. As is typified by a portable telephone or an IC card, electric devices are decreasing in thickness.
As a thin printed wiring board, printed wiring boards using a wholly aromatic polyamide paper as a base material and printed wiring boards using a polyimide film are increasing.
Further, a ceramic substrate also needs to have a thickness of 0.2 mm or less, 0.1 mm, 0.05 mm, 0.03 mm, etc. However, generally, a ceramic is hard and the shape thereof is not altered. Ceramics other than exceptions such as a flexible thin glass plate have a problem that ceramics crack easily when thinned. For this reason, for example, the maximum work size of a ceramic substrate according to a thin film method is a thickness of 0.2 mm and a size of 50 mmxc3x9750 mm.
Similarly, an electronic part itself is decreasing in thickness. The decrease in thickness results from requirements of miniaturization and performance-enhancement.
In view of productivity improvement, developments of a silicon wafer (metal: Si) for enlarging the work size thereof from 8 inches to 12 inches are vigorously being made. Since there is no method for forming electronic circuits including metal on both surfaces concurrently in the current production step, it is required to form electronic circuits on one surface and then form electronic circuits on the other surface. Further, a thermal expansion coefficient difference between metal to be used such as copper or aluminum and a semiconductor substrate is large, e.g., 10xcx9c15xc3x9710xe2x88x926Kxe2x88x921. When electronic circuits are formed on a semiconductor substrate which has been already thinned, warps occur so that in some cases it is impossible to carry out the next step or breakage occurs.
When a semiconductor part in which semiconductor circuits are formed on both surfaces of a thin semiconductor substrate is produced, it is required to adopt a production method in which after the formation of a semiconductor or other electronic circuits at high temperatures, including the introduction of impurities, on one surface (front surface or surface A) of a semiconductor substrate having a general thickness, the above one surface is brought into intimate contact with a holding substrate and held on the holding substrate to protect the one surface, the exposed opposite surface (back surface or surface B) is polished to thin the semiconductor substrate, then semiconductor circuits for the back surface are formed as required, and the semiconductor substrate is separated from the holding substrate and then cut to a chip size or the semiconductor substrate is cut to obtain respective pieces of a chip size and then the respective pieces are separated from the holding substrate.
As a patent concerning the thinning of a semiconductor substrate such as a silicon wafer, there is an example, as shown in JP-A-7-169723, in which wax is heated at 80 to 150xc2x0 C. and melted on a glass substrate, a wafer is attached to the glass substrate with a press, the wafer is polished, then the wafer on the glass substrate is heated to melt the wax and the wafer and the glass substrate are respectively pulled in directions different from each other to separate the wafer. However, this method can not endure a step of a gold vapor deposition or the like.
Further, as a material used for holding for cutting, an UV irradiation peeling type tape and a heat peeling type tape are commercially available. However, these tapes can not endure a step of a gold vapor deposition or the like.
When the step for forming electronic circuits for the back surface is only a metallization for balancing a thermal expansion coefficient or for maintaining strength, a high temperature treatment step is not specially required. However, when semiconductor circuits are formed, a high temperature of approximately 350xc2x0 C. or higher is required and it is required to carry out a holding operation under such a vacuum that a plasma treatment or ion plating at the above high temperature is possible.
Further, even when no high temperature treatment is required, the kind of a usable bonding agent or the kind of a holding substrate are greatly limited depending upon chemicals to be used.
Furthermore, since the semiconductor substrate is fragile, there is necessarily required a method which causes no cracks at a step of bonding and,holding the semiconductor substrate to/on the holding substrate and at a step of separating the semiconductor substrate from the holding substrate.
It is extremely difficult to find a means which overcomes the above problems at the same time.
From this respect, for example, when a highly reproducible bond and hold method is developed, a highly reliable bonding and holding restricted to a necessary period of time or a necessary step and a following easy separation are enabled by a selection of conditions. Further, when the range of usable materials for bonding is broadened, the selection possibility of an appropriate balance between necessary physical properties and separability is considerably broadened.
Further, when the practice of each method is established as a more reproducible method requiring any particular skills by developing a device therefor, the road to mass production can be opened.
It is an object of the present invention to provide a separating machine which can separate a thinned semiconductor substrate from a substrate to which the semiconductor substrate has been bonded without any cracks and a highly reproducible separating method.
According to the present invention, first, there is provided a separating machine for a thinned semiconductor substrate, which separating machine separates a thinned semiconductor substrate from a holding substrate after a semiconductor substrate is bonded to the holding substrate with a thermoplastic resin and a back surface treatment including the thinning of the semiconductor substrate is carried out and which separating machine comprises a pair of vacuum adsorption heads for adsorbing the holding substrate-bonded thinned semiconductor substrate respectively from the holding substrate side and from the thinned semiconductor substrate side opposite to the holding substrate side, wherein at least one of the vacuum adsorption heads has a moving means for adsorbing and holding the holding substrate-bonded thinned semiconductor substrate in a predetermined position together with the other vacuum adsorption head and at least one of the vacuum adsorption heads has a system for moving in a single swing direction for separation after the above adsorption and holding.
Further, in the separating machine for a thinned semiconductor substrate provided according to the present invention, a system for making a starting point (lead) for the separation is provided at the single swing side of the vacuum adsorption head.
Further, in the separating machine for a thinned semiconductor substrate provided according to the present invention, the starting point for the separation is formed at an orientation-flat portion.
Further, in the separating machine for a thinned semiconductor substrate provided according to the present invention, the system for making a starting point for the separation is a system of pressing with a knife edge.
Further, in the separating machine for a thinned semiconductor substrate provided according to the present invention, the system for making a starting point for the separation is composed of a gentle curved surface at at least the single swing side of the vacuum adsorption head and the curved surface adsorbs the holding substrate-attached thinned semiconductor substrate to generate a bending stress.
Secondary, according to the present invention, there is provided a method of separating a thinned semiconductor substrate, comprising bonding and holding a semiconductor substrate to/on the surface of a holding substrate with a thermoplastic resin, carrying out a back surface treatment of the semiconductor substrate, the back surface treatment including the thinning of the semiconductor substrate, and then separating the thinned semiconductor substrate from the holding substrate, wherein the holding substrate-bonded thinned semiconductor substrate is adsorbed and held with a pair of vacuum adsorption heads from the holding substrate side and from the thinned semiconductor substrate side opposite to the holding substrate side, a starting point (lead) for separation from one end side of the bonding portion of the holding substrate-bonded thinned semiconductor substrate is made, and the vacuum head is moved in an opening direction from the starting point (lead) to separate the thinned semiconductor substrate from the holding substrate.
Further, in the method of separating a semiconductor substrate, provided according to the present invention, the holding substrate-bonded thinned semiconductor substrate is immersed in an aqueous solution which is composed of a separating solution containing water as a main ingredient and which has a temperature of 25 to 140xc2x0 C.
Further, in the method of separating a semiconductor substrate, provided according to the present invention, when an aluminum thin film is present on an exposed portion of the thinned semiconductor substrate, the separating solution contains silicon (Si) in an amount of at least 1 mol/l.